Viscous damper with means preventing sidewall deflection

ABSTRACT

A clutch plate assembly (24) for a vehicle driveline includes a spring damping mechanism disposed in a parallel with a viscous shear damper mechanism (30) for damping spring recoil. The spring damping mechanism includes a set of pairs of relatively high rate helical compression springs (34,36) for transmitting torque and attenuating torsionals when a transmission input shaft (22) is connected to a load and a set of relatively low rate helical compression springs (38) connected in series with the high rate spring (34,36) for attenuating torsionals when the shaft (22) is not connected to a load. The viscous damper mechanism includes an annular housing (48) having first and second radially extending sidewalls (52,54) defining a compartment (48a) having a clutch assembly (50) disposed therein for viscous clutching coaction via a viscous shear oil. An inner member (58) of the clutch assembly (50) includes a dynamic seal assembly (66 or 72) molded integral therewith for sealing the inner extent of the compartment (48a). The inner extent of the housing includes a plurality of fasteners (56e) structurally interconnecting the inner extent of the sidewalls (52,54) to prevent relative axial movement of the sidewalls due to centrifugal effects. The housing sidewalls (52,54), and the clutch and seal assemblies are formed to facilitate a method for readily assembling and accurately filling the damper with viscous shear oil.

CROSS-REFERENCE TO RELATED APPLICATIONS

The invention of this aplications relates to U.S. application Ser. No.793,802, filed November 1, 1985; to U.S. application Ser. No. 256,690,filed October 12, 1988; and to U.S. application Ser. No. 256,816, filedOct. 12, 1988. These applications are asigned to the asignee of thisapplication.

FIELD OF THE INVENTION

This invention relates to torsional vibration damping mechanisms. Morespecifically, this invention relates to a viscous damper module fordamping the rate of spring recoil in a torsion vibration dampingmechanism.

BACKGROUND OF THE INVENTION

Torsional vibration damping mechanisms have long been used to reduce theadverse effects of torsional vibrations or fluctuating torques invehicle drivelines. Such torsional vibrations or fluctuating torques,hereinafter referred to as torsionals, emanate primarily from enginepower pulses and torque spikes, and from abrupt changes in drivelinetorque due primarily to rapid engine acceleration/deceleration andtransmission ratio changes.

Most known, prior art torsional vibration damping mechanisms haveemployed springs disposed in parallel with a mechanical friction device.A well known and basic type of such mechanism has comprised plate likemembers mounted for limited relative rotation, a set of helicalcompression springs interconnecting the members and a mechanicalfriction device responsive to relative rotation of the members.Driveline torque is normallly transmitted by the helical springs andflexing of the springs attenuates or reduces the potential amplitude ofthe driveline torsionals. The mechanical friction device dampens orreduces the rate of spring recoil. When the amplitude of the torsionalsis less than the breakaway torque of the friction device, spring flexingdoes not occur and the torsionals are transmitted without benefit ofattenuation.

It is also known to employ flat spiral wound or helical compressionsprings in parallel with a viscous coupling or damper mechanism, as maybe seen by reference to U.S. Pat. Nos. 4,608,883 and 4,601,676,respectively, which are incorporated herein by reference. Since a liquidis the clutching medium within a viscous damper, the problem ofbreakaway torque associated with mechanical friction devices is intheory eliminated. However, such viscous dampers have been difficult tofit into the limited space available in vehicle dirvelines and whenreduced to sizes that fit in the limited space available, they have beendifficult to assemble and properly fill with viscous shear oil, and theyhave required costly and/or bulky dynamic seal to eliminate seal dragtorque.

SUMMARY OF THE INVENTION

An object of this invention is to provide means for reducing axialseparation of the sidewalls of a viscous coupling or damper due tocentrifugal effects.

According to a feature of the invention, a torsion damping mechanism isadapted for connection between input and output drives of a torquetransmitting driveline. The mechanism includes a spring damper fortransmitting torque between the drives and a viscous damper includingannular housing and clutch assemblies adapted for rotation about therotational axis of one of the drives. The housing assembly includesfirst and second radially extending sidewalls having mutually facingsidewall surfaces defining an annular radially extending compartmentopen at its radially inner extent and closed at its radially outerextent by means sealingly securing the sidewalls together, the housingbeing adapted to be driven by the other drive. The clutch assemblyincludes radially outer and inner portions, the outer portion havingoppositely facing radially extending surfaces disposed in close axiallyspaced relation from the sidewall surfaces for viscous clutchingcoaction therewith via a viscous liquid in the compartment, and theinner portion extending radially inward of the housing for drivingconnection to the one drive. A dynamic seal assembly cooperates betweenthe clutch inner portion and radially inner portion of the housingsidewalls for sealing the radially inner extent of the compartment. Thedamper is characterized by the clutch assembly including a pluralitycircumferentially spaced apart openings extending therethrough and thehousing assembly includes a plurality of fasteners freely extendingthrough said openings and having opposite ends fixed to the housingsidewalls for preventing axial movement of the sidewalls relative toeach other, the circumferentially spaced apart openings having an arclength allowing a predetermined amount of relative rotation between thehousing and clutch assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

The torsional damping mechanism of the present invention is shown in theaccompanying drawings in which:

FIG. 1 is a schematic view of a motor vehicle driveline;

FIG. 2 is a detailed, sectional view of the mechanism looking along line2--2 of FIG. 3;

FIG. 3 is a detailed, sectional view of a viscous damper of themechanism looking along line 3--3 of FIG. 2;

FIG. 4 is an enlarged sectional view of a portion of a seal in themechanism;

FIG. 5 is an enlarged sectional view of a portion of an alternativeseal; and

FIG. 6 is a sectional view of the viscous damper illustrating a methodof assembling and filling the damper with a viscous shear liquid.

DETAILED DESCRIPTION OF THE DRAWINGS

The motor vehicle driveline seen schematically in FIG. 1 includes aprime mover 10 and a transmission 12 having an output shaft 14 drivinglyconnected to a load such as a ground engaging wheel 16 via adifferential gear assembly 18 for rear and/or front axles of a vehicle.Prime mover 10 is preferably of the internal, periodic combustion typebut may be any type of power plant having torque characteristics thatare improved by a torsional vibration damping mechanism. Transmission 12includes a housing 20 containing a plurality of unshown, constant meshratio gears or ratio change mechanisms driven by a tranmission inputshaft or drive 22 partially shown in FIG. 2. Well-known ratio changedevices or clutches within the transmission are employed to selectively(i.e., manually or automatically) put the transmission in a neutralposition wherein the input shaft 22 is not connected to the load orin-gear positions wherein the input shaft is connected to the load.

Looking now at FIGS. 2 and 3, therein is illustrated an annular clutchplate assembly 24 disposed for rotation about the axis of transmissioninput shaft 22. Clutch plate assembly 24 includes a partially shownannular friction ring 26 in driving relation with shaft 22 via a springdamping mechanism 28 positioned radially between the friction ring andshaft 22 and disposed in parallel with a viscous shear damper mechanism30. The friction ring includes oppositely facing friction surfaces26a,26b frictionally connectable to a partially shown engine flywheel 32in response to selective axial movement of an unshown pressure plate inwell-known manner.

The spring damper mechanism 28, which is well-known in the prior art,includes a first set of pairs of springs 34,36 for transmitting fulldriveline torque, a set of gear anti-rattle springs 38, an intermediatemember 40, a hub 42 slidably splined to drive 22, and a supportstructure including annular side plates 44,46. The viscous dampermechanism 30 or module includes annular housing and clutch assemblies48,50. Housing assembly 48 includes first and second radially extendingsidewalls 52,54 and clutch assembly 50 includes radially inner and outermembers 56,58. The sidewalls define an annular radially extendingcompartment 48a closed at its radially outer extent, open at itsradially inner extent and having the clutch assembly inner and outermembers disposed therein. Side plates 44,46 of the support structure arerigidly secured together by a plurality of pins 60. The pins alsorigidly secure friction ring 26 and viscous damper housing assembly 48to the support structure. The ends of the pins are peened over whenassembly is complete. Intermediate member 40 includes a plurality ofcircumferentially spaced apart openings 40a each receiving a pair ofsprings 34,36. The springs are also received by an equal number of pairsof circumferentially spaced apart openings 44a,46a in side plates 44,46.Radially extending ends of openings 40a,44a,46a react against thesprings and connect the spring sets in series. Side plate 44 isjournaled on hub 42 by a plastic bushing 62, intermediated member 40 isloosely splined to hub 42 in the circumferential direction. Anti-rattlesprings 38 resist the free play between the unshown splines of member 40and hub 42. Pins 60 pass through arcuate, circumferentially extendingslots 40b in intermediate member 40 to allow friction ring 26, sideplates 44,46 and viscous damper housing assembly 48 to rotate as a unitrelative to intermediate member 40 and hub 42 in response to flexing ofthe springs 34,36,38.

The viscous damper inner clutch member 56 includes splines 56a whichmate with splines 42a of the hub, whereby a given relative rotationbetween friction ring 26 and hub 42 provides an equal relative rotationbetween viscous damper housing assembly 48 and inner clutch member 56.Housing assembly 48 and clutch assembly 50 define closely spaced apartshear surfaces which are in clutching coaction via viscous shear liquidtherebetween. The viscous shear liquid is of high viscosity and ispreferably a silicone oil, for example dimethyl polysiloxane. The actualviscosity depends on driveline application, area and spacing of thehousing and clutch surfaces, mean radius of the surface areas, etc.

Looking now at viscous damper mechanism 30 in greater detail, annularhousing and clutch assemblies 48,50 are formed of stampings andtherefore are relatively inexpensive to manufacture since they requirelittle or no machining. Further, damping mechanism 30 is designed tofacilitate installation in a limited available space, rapid and accurateassembly in production, and rapid and accurate filling with viscousshear liquid during assembly.

With respect to housing assembly 48, first sidewall 52 includes aradially outer portion defining a flat, annular shear surface 52a, aradially inner portion defining a flat, annular seal surface 52b, anannular bulge 52c, and a plurality of tabs or feet 52d secured to pins60 as previously mentioned. First sidewall 52 also includes a pluralityof axially extending, circumferentially spaced apart tabs or fingers 52eexplained further hereinafter. Sidewall 54 includes a radially outerportion defining a flat, annular shear surface 54a, a radially innerportion defining a flat, annular seal surface 54b, and an annularaxially extending spacer flange 54c sealingly secured to a radiallyouter extent of shear surface 52a and having an axial length definingthe axial distance between shear surfaces 52a,54a.

With respect of clutch assembly 50, outer clutch member 58 includesaxially oppositely facing, flat, annular shear surfaces 58a,58b whichare closely spaced from the sidewall shear surfaces 52a,54a to form aviscous shear chamber 64, generally bounded in the radial direction byspacer flange 54c and the radially outer periphery of annular bulge 52c.The remainder of compartment 48a defines a reservoir chamber 65. Theinner periphery of outer member 58 is drivingly connected to the outerperiphery of inner member 56 via tabs 56b which are received by half ofrecesses 58c. Herein, the arcuate length of recesses 58a is greater thanthat of tabs 56b to allow rotational free play or lost motiontherebetween. Alternatively, the free play may be deleted; however, themating of the tabs and recesses preferably allows axial movement of themember relative to each other for purposes explained hereinafter. Innerclutch member 56 includes, in addition to splines or tabs 56a,56b, aplurality of arcuate surfaces 56c of equal radius journaling the outermember thereon and a dynamic face seal assembly 66 integral with theinner member. The seal assembly is partially shown enlarged in FIG. 4.Dynamic seal, as used herein, means a seal having a portion in sealingrelation with a relatively movable surface.

The seal assembly includes symmetrical face seals 68, 70 each having abase portion 68a, 70a sealingly affixed to axially oppositely facingsurfaces 56d, 56e of the inner clutch member, an axially and radiallyinwardly extending primary seal portion 68b,70b terminating in a lip68c,70c in dynamic sealing contact with sidewall seal surface 52b,54b,and an axially and radially inwardly extending exclusion seal portion68d,70d terminating in a lip 68e,70e also in dynamic sealing contactwith seal surface 52b,54b. The bases of seals 68,70 are preferably, butnot necessarily, joined by extrusion of the elastomeric material througha plurality of openings 56f in the clutch inner member during themolding process. Primary seal portions 68b,70b prevent egress or leakageof fluid from housing compartment 48a of the damper mechanism. Exclusionseal portions 68d, 70d prevent ingress of abrasive contaminants to thelips of the primary seal when the damper is used in relatively dryenvironments or of pressurized fluid when the damper is used in, forexample, a torque converter housing. When the exclusion seals areunlubricated, their axial length is preferable less than that of theprimary seals, to reduce seal drag torque and wear.

Further with respect to dynamic sealing of viscous damper andparticularly a damper housing having relatively thin sidewalls, such assidewalls 52,54, it has been found that the sidewalls separate axiallydue to centrifugal effects, thereby increasing the need for greaterminimum amounts of initial or static seal compression to ensure sealingas the housing separates due to centrifugal effects. Such greaterminimum seal compression increases seal drag torque at low rotationalspeeds and, in combination with seal compression added by manufacturingtolerance can result in excessively high seal drag torque, reduced seallife, and poor performance of the spring and viscous damper. Axialseparation of the housing sidewalls is prevented and manufacturingtolerances are reduced, particularly in the area of seal surfaces52b,54b, by structurally connecting the radially inner extent of thesidewalls together by a plurality of circumferentially spaced apartfasteners fingers or spacers 52e defined by tabs extending axially fromsidewall 52 and secured to sidewall 54 by known means such as welding.The tabs extend through circumferentially extending openings 53 betweensplines 42a,56a of hub 42 and inner clutch member 56.

FIG. 5 illustrates an enlarged cross-section of a portion of analternative molded seal assembly 72 including face seals 74,76 eachhaving extended primary and exclusion seal portions 74a,74b, and 76a,76bto further reduce seal drag torque. Molded seal assemblies 66 and 72simplify assembly of the damper mechanism since they are intergral withthe clutch assembly and therefore are installed and properly positionedin one operational step with the clutch assembly. The molded sealassemblies are also axially compact while still being very flexible inthe axial direction; hence, they reduce the axial space necessary toprovide reliable sealing while at the same time reducing the effects ofmanufacturing tolerances which substantially vary seal compression andmay dramatically increase seal drag torque. Further, the feature of anexclusion seal also protects the primary seal from early or prematurefailure due to abrasive contaminants.

Looking now at FIG. 6, therein is illustrated a method of assembling andrapidly filling damper mechanism 30 with a predetermined volume ofsilicone oil sufficient to ensure that thermal expansion of the oil doesnot over fill compartment 48a when the compartment volume is a minimumdue to manufacturing tolerances and the oil volume is a maximum due tomeasuring tolerances, and to ensure a full fill of the shear chamber 64when the shear volume is a maximum due to manufacturing tolerances andthe oil volume is a minimum due to measuring tolerances.

Assembling and filling include positioning sidewall 52 of housing 48 ona support 78 with shear and seal surfaces 52a,52b facing upward and in ahorizontal plane. Clutch assembly 50 is then positioned over sidewall 52with seal 70 of seal assembly 66 resting on seal surface 52b and outermember shear surface 58a resting on sidewall shear surface 52a, therebydefining a trapped volume excessible via openings 58c between the innerand outer clutch members. This trapped volume, by design, has a capacitysufficient to receive the above mentioned predetermined volume ofsilicone oil for all tolerance conditions mentioned above withoutoverflowing the upper surfaces 56a, 58d of inner and outer members56,58. The silicone is readily injected into the trapped volume throughopenings 58c which are not receiving one of the splines or tabs 56b ofthe inner member. Sidewall 54 is then positioned with spacer flange 54cseated on a radially outer extent of shear surface 52a. The interface ofthe spacer flange and shear surface are then sealingly secured togetherby known methods. Since the silicone oil, contained in the trappedvolume, is spaced a substantial distance from spacer flange 54c, any ofseveral rapid welding methods may be used, e.g., resistance or laserwelding.

A preferred embodiment of the invention has been disclose forillustrative purposes. Many variations and modifications of thepreferred embodiment are believed to be within the spirit of theinvention. The following claims are intended to cover the inventiveportions of the preferred embodiment and variations and modificationswithin the spirit of the invention.

What is claimed is:
 1. A torsion damping mechanism adapted forconnection between input and output drives of a torque transmittingdriveline; the mechanism comprising resilient means for drivinglyinterconnecting the drives and a viscous damper including annularhousing and clutch assemblies adapted for rotation about a rotationalaxis of one of the drives; the housing assembly including first andsecond radially extending sidewalls having mutually facing sidewallsurfaces defining an annular radially extending compartment having anopen radially inner extent and a radially outer extent closed by meanssealingly securing the sidewalls together, the housing adpated to bedriven by one of the drives; the clutch assembly including radiallyouter and inner and portions, the outer portion having oppositely facingradially extending surfaces disposed in close axially spaced relationfrom the sidewall surfaces for viscous clutching coaction therewith viaa viscous liquid in the compartment, the inner portion extendingradially inward of the housing for driving connection to the one drive;dynamic seal means cooperating between the clutch inner portion andradially inner portions of the housing sidewalls for sealing theradially inner extent of the compartment; characterized by:the clutchassembly including a plurality of circumferentially spaced apartopenings extending therethrough; and the housing assembly having meansincluding a plurality of fasteners freely extending through saidopenings and having opposite ends fixed to the housing sidewalls forpreventing axial movement of the sidewalls relative to each other, thecircumferentially spaced apart openings having an arc length allowing apredetermined amount of relative rotation between the housing and clutchassemblies.
 2. The mechanism of claim 1, wherein said openings andfasteners are positioned between the seal means and the radially innerextent of the clutch assembly inner portion.
 3. The mechanism of claim1, wherein the first and second sidewalls of the housing assembly eachhave a radially extending seal surface axially facing and spaced fromoppositely facing surfaces of the clutch inner portion; anda face sealformed of elastomeric material molded to each oppositely facing surfaceof the clutch inner portion, each seal having a base portion in staticsealing relation with the associated inner portion surface, and eachseal having a primary seal portion extending axially away from andradially outward from the base portion and terminating in a lip indynamic sealing relation with the associated sidewall seal surface. 4.The mechanism of claim 3, wherein each molded seal also includes anexclusion seal portion extending axially away from and radially inwardfrom the base portion and terminating in a lip in dynamic sealingrelation with the associated sidewall seal surface.
 5. The mechanism ofclaim 4, wherein the oppositely facing surfaces of the innner portioninclude a plurality of circumferentially spaced apart openingstherethrough for joining the bases of the seals via elastomeric materialextruded into the openings during molding of the seals.
 6. A viscousshear mechanism including annular housing and clutch assemblies adaptedfor relative rotation about a common axis; the housing assemblyincluding first and second annular, radially extending sidewalls havingmutually facing sidewall surfaces defining an annular radially extendingcompartment; means sealing and securing the sidewalls against relativerotation and axial movement at the radially outer extend of thecompartment; the clutch assembly including radially inner and outerportions, the outer portion having oppositely facing radially extendingsurfaces disposed in close axially spaced relation from the sidewallsurfaces for viscous clutching coaction therebetween via a viscous shearliquid in the compartment, the inner portion extending radially inwardof the housing for connection to a drive; axially facing dynamic sealmeans cooperating between radially inner portions of the sidewalls andoppositely facing sides of the clutch assembly for closing the radiallyinner extent of the compartment; characterized by:the clutch assemblyincluding a plurality of circumferentially spaced apart openingsextending axially therethrough; and means for preventing relative axialmovement of the radially inner portions of the sidewalls, the means forpreventing including a plurality of fingers extending axially betweenthe sidewalls and freely through the clutch assembly openings, theopenings having arc lengths allowing a predetermined amount of relativerotation between the clutch assembly and the fingers.
 7. The mechanismof claim 6, wherein the fingers are disposed radially inward of thedynamic seal means.
 8. The mechanism of claim 6, wherein the fingers areaffixed to the sidewalls.
 9. The mechanism of claim 6, wherein dynamicseal means include first and second face seals each having a baseportion in static sealing relation with one of the opposite sides of theclutch assembly and each having a lip in dynamic sealing relation withthe radially inner portion of the sidewalls.
 10. The mechanism of claim9, wherein the first and second seals each include a primary sealportion extending axially away from and radially outward from the baseportion and terminating in the lip.
 11. The mechanism of claim 10,wherein the first and second seals each include an exclusion sealportion extending axially away from and radially inward from the baseportion and terminating in a lip in dynamic sealing relation with theradially inner portions of the sidewalls.
 12. The mechanism of claim 6,further including a spring damper having an input affixed to the annularhousing assembly and an output connected to the drive which is connectedto the clutch assembly inner portion.
 13. The mechanism of claim 12,wherein the spring damper includes relatively stiff spring means fortransmitting and attenuating torque between the input and output whenthe output is connected to a load, and relative less stiff spring meansdisposed in series with the stiff spring means and for attenuatingtorque between the drives when the output is not connected to a load.14. The mechanism of claim 7, wherein the fingers are affixed to thesidewalls.
 15. The mechanism of claim 7, wherein dynamic seal meansinclude first and second face seals each having a base portion in staticsealing relation with one of the opposite sides of the clutch assemblyand each having a lip in dynamic sealing relation with the radiallyinner portion of the sidewalls.
 16. The mechanism of claim 15, whereinthe first and second seals each include a primary seal portion extendingaxially away from and radially outward from the base portion andterminating in the lip.
 17. The mechanism of claim 16, wherein the firstand second seals each include an exclusion seal portion extendingaxially from and radially inward from the base portion and terminatingin a lip in dynamic sealing relation with the radially inner portions ofthe sidewalls.
 18. The mechanism of claim 7, further including a springdamper having an input affixed to the annular housing assembly and anoutput connected to the drive which is connected to the clutch assemblyinner portion.
 19. The mechanism of claim 18, wherein the spring damperincludes relatively stiff spring means for transmitting and attenuatingtorque between the input and output when the output is connected to aload, and relative less stiff spring means disposed in series with thestiff spring means and for attenuating torque between the drives whenthe output is not connected to a load.